Another way to solve the problem would be to use the same steps from one of
Jeannie Sandoval's lessons on IAD, "Digital Self Portraits".

1. You could use the digital camera or scan a color photo into Photoshop.
2. Click "Image" and go to "Mode" and change the photo to "gray scale".
Click OK when it asks you about discarding color info. That makes the image
black and white.
3. Then click on "Image" again and go to "Adjustments," scroll
to "Brightness and Contrast" and click on it. The more contrast you put in
it, the fewer shades you will get in the final image. You may want to play
with that til you get what you need, click OK when done.
4. Click "Image" again, scroll to "Adjustments" again, and scroll down
to "Posturize" and click on that one. Play with the numbers on this one too,
to see what gives you the best contrast. You may even need to go back and re-
adjust the brightness and contrast to get it to posturize the way you like.
5. If you don't like the background, or something in the composition, just
use the magnetic tool to cut out what you want to keep, and paste it into a
new format. Don't forget to paint the background in before pasting the
cutout portion in.
When it "Posturizes" it breaks up and simplifies the image to look a little
more "painterly" and a little more like a silkscreen pattern.

Hope I helped and didn't confuse you. Adobe Photoshop is an awesome tool to
have in the art classroom. I learn something new about it all the time!
Grace